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Why does basal body temperature rise after ovulation?

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Detailed cross-sectional illustration of a human ovary showing the stages of follicle development, ovulation, and corpus luteum formation, with labeled structures including primordial, primary, secondary, and mature follicles, a ruptured follicle releasing an ovum, and corpus luteum and albicans. An inset at the bottom shows the ovary's location in the female reproductive system. — ovary The steps of ovulation, beginning with a dormant primordial follicle that grows and matures and is eventually released from the ovary into the fallopian tube.

The basal body temperature rise observed after ovulation is caused by the production of progesterone.1

Following ovulation, the ruptured follicle transforms into the corpus luteum, which secretes large amounts of progesterone. This hormone is responsible for increasing a woman’s body temperature by approximately 0.5 °C (1 °F) during the mid-cycle. Because this temperature shift is a direct result of progesterone production, daily tracking of basal body temperature serves as a clinical method to confirm that ovulation has occurred.21